Abstract: ICT is developing rapidly and is playing an increasingly important role in society. High expectations are placed on ICT in relation to sustainable development. In order to provide basis for decision-making and ensure that ICT is used in the best possible way for enabling sustainable development, the sustainability impacts of ICT need to be studied.This thesis aims to provide new knowledge on the environmental impacts related to ICT, to explore the potential of ICT to contribute to sustainability, and discuss ways of assessing environmental impacts of ICT. In order to fulfill the aim a literature review of existing LCA studies of ICT was done, an LCA case study of printed and online media was performed, a methodological framework for sustainability assessment of scenarios was developed and then applied for environmental assessment of future ICT societies.The results show that manufacturing and use phase are the life cycle stages contributing the most to the ICT environmental impacts. For online newspapers online distribution and content production may give significant contribution to the overall impact. User behavior was observed to be crucial for the results of comparisons of ICT solutions with their traditional counterparts.The following key issues were concluded to influence the environmental risks and opportunities in future ICT societies: energy mix, economic conditions, life styles, technology, and environmental ambitions, incentives and regulation. The potential of ICT for sustainability is affected by these key issues.A new methodological framework (SAFS) was developed for the assessment of future scenarios (societal level). Life cycle assessment (LCA) was used for assessment on a product level. Application of both methods, their benefits, drawbacks, and challenges of assessment were discussed. Both types of assessments were concluded to be important to support decision-making.